1. Field of the Invention
The present invention relates to a semiconductor fabrication apparatus that fabricates semiconductor devices. More particularly, the present invention is concerned with a heat treatment apparatus that performs activation annealing or defect repair annealing, which is preceded by doping of an impurity and intended to control the conductivity of a semiconductor substrate, and oxidation or the like of the surface of the semiconductor substrate.
2. Description of the Related Art
In recent years, an expectation has been put on introduction of a novel material having a wide bandgap, such as, silicon carbide (SiC) (or gallium nitride (GaN)) as a substrate material of a power semiconductor device. Since SiC has a wider bandgap than silicon (Si) that is an existing material, if SiC is adopted for a switching device or a Schottky barrier diode that is used to construct an inverter or the like, a dielectric strength can be improved and a leakage current can be minimized accordingly. Eventually, power consumption can be reduced.
A process of fabricating various types of power devices using SiC as a substrate material is almost identical to a process in which Si is used as the substrate material, though the size or the like of the substrate is different between the SiC substrate and Si substrate. As a sole largely different process, a heat treatment process is cited. What is referred to as the heat treatment process is represented by activation annealing that is preceded by ion implantation of an impurity and intended to control the conductivity of the substrate. In the case of a Si device, the activation annealing is performed at the temperature ranging from 800° C. to 1200° C. However, in the case of SiC, the temperature ranging from 1800° C. to 2000° C. is necessary in terms of the material properties.
As an annealing apparatus, a resistive heating furnace described, for example, in Japanese Patent Application Laid-Open Publication No. 2009-32774 is known. Aside from the resistive heating furnace type, an annealing apparatus of an induction heating type described in, for example, Japanese Patent Application Laid-Open Publication No. 2010-34481 is known.